High-temperature creep behavior at 350 °C in laser-welded joints of a novel heat-resistant aluminum alloy Al-12Ce-0.4Sc

This study examines the high-temperature creep behavior of dual-stage heat-treated Al-12Ce-0.4Sc alloy laser welding joints at 350 °C. Under 35 MPa stress, the joints exhibit steady-state creep after 120 h. Reducing stress from 50 MPa to 40 MPa shifts fracture locations from the fusion line to the weld seam. At 350 °C, cracks initiate at the Al₁₁Ce₃ phase, while voids form at the Al-Al₁₁Ce₃ interface. Void growth and crack intersection lead to joint fracture. Post-creep, the average geometric necessary dislocation (GND) density increases significantly in both the base material and weld seam, indicating that the weld seam and the base material areas experienced considerable creep deformation. The true stress index is 4.5, and the creep mechanism involves dislocation slip and grain boundary sliding. Large primary Al₁₁Ce₃ particles are present along the fusion line, with stress concentration observed nearby. Voids in the heat-affected zone adjacent to the fusion line primarily initiate at the Al-Al₁₁Ce₃ interface. Under high stress, voids grow rapidly, intersecting cracks in Al₁₁Ce₃, causing joint fracture at the fusion line. Under low stress, Al₁₁Ce₃ fracture propensity decreases, while voids at the aluminum matrix in the weld seam region connect with micro-cracks in eutectic Al₁₁Ce₃ particles, resulting in joint fracture within the weld seam.